1. Field of the Invention
The invention relates to a bone anchoring device including a bone anchoring element and a receiving part for coupling a rod to the bone anchoring element. The receiving part includes a rod receiving portion for receiving the rod and a head receiving portion that is flexible so as to allow introduction and clamping of a head of the bone anchoring element. The bone anchoring device further includes a locking ring arranged around the head receiving portion that can assume a locking position in which an inserted head is locked by compression of the head receiving portion of the receiving part. The locking ring has an outer surface with an engagement portion for engagement with a tool. The tool is configured to cooperate with the receiving part and the locking ring so as to allow releasing of the locking ring from a position in which the locking ring locks the head. The bone anchoring device can be realized, for example, in the form of a polyaxial bone screw.
2. Description of Related Art
US 200910149887 A1 discloses an apparatus for connecting a bone anchor to a support rod, the apparatus including a connector body and a cap. The connector body has a socket for insertion, angulation and removal of a bone anchor. A sleeve is provided, which is configured to fit over the connector body in a temporary position, in which the sleeve permits insertion of the bone anchor, to move to a provisional locking position, in which the sleeve permits angulation but prevents removal of the bone anchor, and to move to a locking position in which the sleeve prevents both angulation and removal of the bone anchor. Tools are provided for installing the connector body, the sleeve, a cap and the support rod.